This invention relates to a superconductor junction material having an oxide substrate provided with one or more flux flow elements and, optionally, one or more Josephson junction elements and to a process for the production thereof.
In application of superconductors to electronic devices, it is very important to produce Josephson junctions with a large IcRn product. Because high Tc oxide superconductors have layered crystal structures and short coherent lengths, it is very difficult to produce Josephson junctions of a laminate type. Thus, the recent trend in the fabrication of Josephson junctions is toward the formation of grain boundary on a substrate.
Gross, R. et al propose the use of a substrate which is a laminate of two single crystal layers (Phys. Rev. Lett., 64, 228 (1990)). Dary, K. et al propose the use of a substrate having a stepped portion (Appl. Phys. Lett., 58, 543 (1991)). These methods, which utilize the difference in crystal orientations of the superconductors on both sides of the link, are not satisfactory because of the poor reproducibility of the Josephson junction characteristics, a small IcRn product and difficulty in forming the link at a desired position.
Neumann, C. et al propose a YBaCuO Josephson junctions produced by a method in which a YBaCuO film is grown on a MgO substrate which has been damaged with a focused Ga-ion beam to form a weak link (Jpn. J. Appl. Phys., 32, No. 2, L727-L729 1993) and Physica C, 210, 138-146 (1993)). This method permits the formation of a Josephson junction on a desired area on a substrate with good reproducibility and with a high degree of precision.